System, apparatus and method for loose lock-step redundancy power management

ABSTRACT

A processor includes a plurality of cores, at least two of which may execute redundantly, a configuration register to store a first synchronization domain indicator to indicate that a first core and a second core are associated with a first synchronization domain, and a power controller having a synchronization circuit to cause a dynamic adjustment to a frequency of at least one of the first and second cores to cause these cores to operate at a common frequency, based at least in part on the first synchronization domain indicator.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.17/210,759, filed Mar. 24, 2021, now U.S. Pat. No. 11,402,891, issuedAug. 2, 2022, which is a continuation of U.S. patent application Ser.No. 16/663,645, filed Oct. 25, 2019, now U.S. Pat. No. 10,990,154,issued Apr. 27, 2021, which is a continuation of U.S. patent applicationSer. No. 16/546,441, filed Aug. 21, 2019, now U.S. Pat. No. 10,963,034,issued Mar. 30, 2021, which is a continuation of U.S. patent applicationSer. No. 15/635,307, filed Jun. 28, 2017, now U.S. Pat. No. 10,429,919,issued Oct. 1, 2019 the content of which is hereby incorporated byreference.

TECHNICAL FIELD

Embodiments relate to power management of a system, and moreparticularly to power management of a multicore processor.

BACKGROUND

Advances in semiconductor processing and logic design have permitted anincrease in the amount of logic that may be present on integratedcircuit devices. As a result, computer system configurations haveevolved from a single or multiple integrated circuits in a system tomultiple hardware threads, multiple cores, multiple devices, and/orcomplete systems on individual integrated circuits. Additionally, as thedensity of integrated circuits has grown, the power requirements forcomputing systems (from embedded systems to servers) have alsoescalated. Furthermore, software inefficiencies, and its requirements ofhardware, have also caused an increase in computing device energyconsumption. In fact, some studies indicate that computing devicesconsume a sizeable percentage of the entire electricity supply for acountry, such as the United States of America. As a result, there is avital need for energy efficiency and conservation associated withintegrated circuits. These needs will increase as servers, desktopcomputers, notebooks, Ultrabooks™ tablets, mobile phones, processors,embedded systems, etc. become even more prevalent (from inclusion in thetypical computer, automobiles, and televisions to biotechnology.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a portion of a system in accordance with anembodiment of the present invention.

FIG. 2 is a block diagram of a processor in accordance with anembodiment of the present invention.

FIG. 3 is a block diagram of a multi-domain processor in accordance withanother embodiment of the present invention.

FIG. 4 is an embodiment of a processor including multiple cores.

FIG. 5 is a block diagram of a micro-architecture of a processor core inaccordance with one embodiment of the present invention.

FIG. 6 is a block diagram of a micro-architecture of a processor core inaccordance with another embodiment.

FIG. 7 is a block diagram of a micro-architecture of a processor core inaccordance with yet another embodiment.

FIG. 8 is a block diagram of a micro-architecture of a processor core inaccordance with a still further embodiment.

FIG. 9 is a block diagram of a processor in accordance with anotherembodiment of the present invention.

FIG. 10 is a block diagram of a representative SoC in accordance with anembodiment of the present invention.

FIG. 11 is a block diagram of another example SoC in accordance with anembodiment of the present invention.

FIG. 12 is a block diagram of an example system with which embodimentscan be used.

FIG. 13 is a block diagram of another example system with whichembodiments may be used.

FIG. 14 is a block diagram of a representative computer system.

FIG. 15 is a block diagram of a system in accordance with an embodimentof the present invention.

FIG. 16 is a block diagram illustrating an IP core development systemused to manufacture an integrated circuit to perform operationsaccording to an embodiment.

FIG. 17 is a flow diagram of a method in accordance with an embodimentof the present invention.

FIG. 18 is a flow diagram of a method in accordance with anotherembodiment of the present invention.

FIG. 19 is a block diagram of a system in accordance with an embodimentof the present invention.

FIG. 20 is a block diagram of a system in accordance with anotherembodiment of the present invention.

DETAILED DESCRIPTION

In various embodiments, a processor may be controlled with techniques toenable multiple cores or other processing engines of the processor tooperate in a loose lock-step manner with regard to performance state(P-state) management, e.g., for applications using software-basedredundancy. In this way, cores in redundant execution can performredundancy checks in a timely and power efficient manner. Still further,this loose lock-step P-state control can be performed dynamically duringprocessor execution such that cores can dynamically enter into and exitfrom common P-state control, as described herein.

In some cases, this loose lock-step P-state control can be used duringexecution of compute applications that have functional safety (FuSa)requirements. In such cases, FuSa requirements may be met withoutincurring the expense and overhead of other techniques such as arrayerror correction coding (ECC), end-to-end bus parity, etc. Stillfurther, using an embodiment as described herein, redundant operationcan be realized without complicated lockstep operation. In this way,power management operations, which may constantly change voltage andfrequency of cores according to changing ambient conditions, workloadand system configuration, can occur on cores involved in redundantexecution, without setting a fixed frequency to the cores. Note that asused herein, the term “redundant execution” or similar terms includesexecution of the same code on multiple cores or other processingengines, and further includes execution of different codecollaboratively on such multiple cores or processing engines, forexample, by way of execution of main code and checker code.

More specifically, loose lock-step P-state control may occur by enablingcores to operate dynamically, either with per core P-state (PCPS)control or loose lock-step control in which multiple cores can bedynamically controlled to operate with a given P-state such that acluster of cores are controlled to operate at the same frequency. Notethat even with loose lock-step control as described herein, other coresof a processor may operate at independent P-states. In some embodiments,loose lock-step control may be realized by sending the same performancestate command (e.g., via a broadcast message) concurrently to a selectedset of cores within a given domain or cluster. Note that this commanddoes not guarantee cycle accurate synchronization, and some variance dueto internal communication is acceptable. In embodiments, this variancemay be bounded to guarantee proper functionality. In other embodimentscycle accurate synchronization may occur.

As described herein, the term “synchronization domain” is used to referto a collection of multiple cores or other processing engines that aredynamically controlled to operate at the same (or substantially) thesame frequency and/or voltage, in response to a given condition.However, understand that this synchronization domain does notnecessarily correspond to a “power domain,” which is collection of coresor other processing engines having a physical relationship and arestatically controlled to operate at least at the same frequency point(and possibly same voltage). This is the case, as instead thissynchronization domain is a dynamically controllable capability that mayflexibly be enabled and disabled during runtime based on the givencondition. Note also that while these cores or other processing enginesare controlled to operate with (at least) substantially the sameoperating parameters, this control is performed in a loose lock-stepmanner, such that any changes or updates to frequency and/or voltage maynot occur identically or concurrently, and instead may occur within arelatively small time duration. In embodiments this time duration maybe, e.g., a bounded or predetermined number of execution cycles. Forexample, this bounded number of execution cycles may range betweenapproximately 1 and 10,000 cycles, to ensure that redundantly executedtasks, strands, threads or so forth execute at least substantiallycontemporaneously on two or more cores or other processing engines. Inthis way, results (including interim results) may be returned within arelatively small time window (e.g., within a predetermined minimal boundof execution cycles), so that identical (or at least substantiallyidentical) results may be confirmed and further execution is allowed toproceed.

In one embodiment, an example architectural interface to communicate thesynchronization domain capability and control can implemented within ahardware P-state (HWP) thread-level machine specific register (MSR),such as by way of a synchronization domain field of this register. Insuch an embodiment, this register may be written at schedule time of agiven thread. In this use case, a 4-bit field (for example) can supportup to 15 synchronization domains (with a default value of, e.g., zero,to indicate that the core is not a member of any synchronizationdomain). In an alternate embodiment, a single package MSR can beprovided with (e.g.,) a 4-bit domain field per core. In such cases, ineach schedule period, a scheduler such as an operating system (OS)scheduler updates the core MSR with the domain notification. This datais transferred to a power controller, which, responsive to such update,may trigger the synchronization frequency control during a powermanagement evaluation.

Although the following embodiments are described with reference toenergy conservation and energy efficiency in specific integratedcircuits, such as in computing platforms or processors, otherembodiments are applicable to other types of integrated circuits andlogic devices. Similar techniques and teachings of embodiments describedherein may be applied to other types of circuits or semiconductordevices that may also benefit from better energy efficiency and energyconservation. For example, the disclosed embodiments are not limited toany particular type of computer systems. That is, disclosed embodimentscan be used in many different system types, ranging from servercomputers (e.g., tower, rack, blademicro-server and so forth),communications systems, storage systems, desktop computers of anyconfiguration, laptop, notebook, and tablet computers (including 2:1tablets, phablets and so forth), and may be also used in other devices,such as handheld devices, systems on chip (SoCs), and embeddedapplications. Some examples of handheld devices include cellular phonessuch as smartphones, Internet protocol devices, digital cameras,personal digital assistants (PDAs), and handheld PCs. Embeddedapplications may typically include a microcontroller, a digital signalprocessor (DSP), network computers (NetPC), set-top boxes, network hubs,wide area network (WAN) switches, wearable devices, or any other systemthat can perform the functions and operations taught below. More so,embodiments may be implemented in mobile terminals having standard voicefunctionality such as mobile phones, smartphones and phablets, and/or innon-mobile terminals without a standard wireless voice functioncommunication capability, such as many wearables, tablets, notebooks,desktops, micro-servers, servers and so forth. Moreover, theapparatuses, methods, and systems described herein are not limited tophysical computing devices, but may also relate to softwareoptimizations for energy conservation and efficiency. As will becomereadily apparent in the description below, the embodiments of methods,apparatuses, and systems described herein (whether in reference tohardware, firmware, software, or a combination thereof) are vital to a‘green technology’ future, such as for power conservation and energyefficiency in products that encompass a large portion of the US economy.

Referring now to FIG. 1 , shown is a block diagram of a portion of asystem in accordance with an embodiment of the present invention. Asshown in FIG. 1 , system 100 may include various components, including aprocessor 110 which as shown is a multicore processor. Processor 110 maybe coupled to a power supply 150 via an external voltage regulator 160,which may perform a first voltage conversion to provide a primaryregulated voltage Vreg to processor 110.

As seen, processor 110 may be a single die processor including multiplecores 120 a-120 n. In addition, each core may be associated with anintegrated voltage regulator (IVR) 125 a-125 n which receives theprimary regulated voltage and generates an operating voltage to beprovided to one or more agents of the processor associated with the IVR.Accordingly, an IVR implementation may be provided to allow forfine-grained control of voltage and thus power and performance of eachindividual core. As such, each core can operate at an independentvoltage and frequency, enabling great flexibility and affording wideopportunities for balancing power consumption with performance. In someembodiments, the use of multiple IVRs enables the grouping of componentsinto separate power planes, such that power is regulated and supplied bythe IVR to only those components in the group. During power management,a given power plane of one IVR may be powered down or off when theprocessor is placed into a certain low power state, while another powerplane of another IVR remains active, or fully powered. Similarly, cores120 may include or be associated with independent clock generationcircuitry such as one or more phase lock loops (PLLs) to controloperating frequency of each core 120 independently.

Still referring to FIG. 1 , additional components may be present withinthe processor including an input/output interface (IF) 132, anotherinterface 134, and an integrated memory controller (IMC) 136. As seen,each of these components may be powered by another integrated voltageregulator 125 x. In one embodiment, interface 132 may enable operationfor an Intel® Quick Path Interconnect (QPI) interconnect, which providesfor point-to-point (PtP) links in a cache coherent protocol thatincludes multiple layers including a physical layer, a link layer and aprotocol layer. In turn, interface 134 may communicate via a PeripheralComponent Interconnect Express (PCIe™) protocol.

Also shown is a power control unit (PCU) 138, which may includecircuitry including hardware, software and/or firmware to perform powermanagement operations with regard to processor 110. As seen, PCU 138provides control information to external voltage regulator 160 via adigital interface 162 to cause the voltage regulator to generate theappropriate regulated voltage. PCU 138 also provides control informationto IVRs 125 via another digital interface 163 to control the operatingvoltage generated (or to cause a corresponding IVR to be disabled in alow power mode). In various embodiments, PCU 138 may include a varietyof power management logic units or circuits to perform hardware-basedpower management. Such power management may be wholly processorcontrolled (e.g., by various processor hardware, and which may betriggered by workload and/or power, thermal or other processorconstraints) and/or the power management may be performed responsive toexternal sources (such as a platform or power management source orsystem software). PCU 138 may be configured to control multiple cores orother processing circuits to dynamically enter into and exit fromsynchronization domains such that these collection of circuits canoperate in a loose lock-step manner as to P-states, as described herein.

In FIG. 1 , PCU 138 is illustrated as being present as a separatecircuit of the processor. In other cases PCU 138 may execute on a givenone or more of cores 120. In some cases, PCU 138 may be implemented as amicrocontroller (dedicated or general-purpose) or other control logicconfigured to execute its own dedicated power management code, sometimesreferred to as P-code. In yet other embodiments, power managementoperations to be performed by PCU 138 may be implemented externally to aprocessor, such as by way of a separate power management integratedcircuit (PMIC) or other component external to the processor. In yetother embodiments, power management operations to be performed by PCU138 may be implemented within BIOS or other system software.

Embodiments may be particularly suitable for a multicore processor inwhich each of multiple cores can operate at an independent voltage andfrequency point. As used herein the term “domain” is used to mean acollection of hardware and/or logic that operates at the same voltageand frequency point. In addition, a multicore processor can furtherinclude other non-core processing engines such as fixed function units,graphics engines, and so forth. Such processor can include independentdomains other than the cores, such as one or more domains associatedwith a graphics engine (referred to herein as a graphics domain) and oneor more domains associated with non-core circuitry, referred to hereinas an uncore or a system agent. Although many implementations of amulti-domain processor can be formed on a single semiconductor die,other implementations can be realized by a multi-chip package in whichdifferent domains can be present on different semiconductor die of asingle package.

While not shown for ease of illustration, understand that additionalcomponents may be present within processor 110 such as uncore logic, andother components such as internal memories, e.g., one or more levels ofa cache memory hierarchy and so forth. Furthermore, while shown in theimplementation of FIG. 1 with an integrated voltage regulator,embodiments are not so limited. For example, other regulated voltagesmay be provided to on-chip resources from external voltage regulator 160or one or more additional external sources of regulated voltages.

Note that the power management techniques described herein may beindependent of and complementary to an operating system (OS)-based powermanagement (OSPM) mechanism. According to one example OSPM technique, aprocessor can operate at various performance states or levels, so-calledP-states, namely from P0 to PN. In general, the P1 performance state maycorrespond to the highest guaranteed performance state that can berequested by an OS. In addition to this P1 state, the OS can furtherrequest a higher performance state, namely a P0 state. This P0 state maythus be an opportunistic, overclocking, or turbo mode state in which,when power and/or thermal budget is available, processor hardware canconfigure the processor or at least portions thereof to operate at ahigher than guaranteed frequency. In many implementations a processorcan include multiple so-called bin frequencies above the P1 guaranteedmaximum frequency, exceeding to a maximum peak frequency of theparticular processor, as fused or otherwise written into the processorduring manufacture. In addition, according to one OSPM mechanism, aprocessor can operate at various power states or levels. With regard topower states, an OSPM mechanism may specify different power consumptionstates, generally referred to as C-states, C0, C1 to Cn states. When acore is active, it runs at a C0 state, and when the core is idle it maybe placed in a core low power state, also called a core non-zero C-state(e.g., C1-C6 states), with each C-state being at a lower powerconsumption level (such that C6 is a deeper low power state than C1, andso forth). Note that using the demotion-based techniques herein, C-staterequests from the OS can be overridden, based at least in part oncustomer tuning information provided via an interface as describedherein.

Understand that many different types of power management techniques maybe used individually or in combination in different embodiments. Asrepresentative examples, a power controller may control the processor tobe power managed by some form of dynamic voltage frequency scaling(DVFS) in which an operating voltage and/or operating frequency of oneor more cores or other processor logic may be dynamically controlled toreduce power consumption in certain situations. In an example, DVFS maybe performed using Enhanced Intel SpeedStep™ technology available fromIntel Corporation, Santa Clara, Calif., to provide optimal performanceat a lowest power consumption level. In another example, DVFS may beperformed using Intel TurboBoost™ technology to enable one or more coresor other compute engines to operate at a higher than guaranteedoperating frequency based on conditions (e.g., workload andavailability).

Another power management technique that may be used in certain examplesis dynamic swapping of workloads between different compute engines. Forexample, the processor may include asymmetric cores or other processingengines that operate at different power consumption levels, such that ina power constrained situation, one or more workloads can be dynamicallyswitched to execute on a lower power core or other compute engine.Another exemplary power management technique is hardware duty cycling(HDC), which may cause cores and/or other compute engines to beperiodically enabled and disabled according to a duty cycle, such thatone or more cores may be made inactive during an inactive period of theduty cycle and made active during an active period of the duty cycle.

Power management techniques also may be used when constraints exist inan operating environment. For example, when a power and/or thermalconstraint is encountered, power may be reduced by reducing operatingfrequency and/or voltage. Other power management techniques includethrottling instruction execution rate or limiting scheduling ofinstructions. Still further, it is possible for instructions of a giveninstruction set architecture to include express or implicit direction asto power management operations. Although described with these particularexamples, understand that many other power management techniques may beused in particular embodiments.

Embodiments can be implemented in processors for various marketsincluding server processors, desktop processors, mobile processors andso forth. Referring now to FIG. 2 , shown is a block diagram of aprocessor in accordance with an embodiment of the present invention. Asshown in FIG. 2 , processor 200 may be a multicore processor including aplurality of cores 210 a-210 n. In one embodiment, each such core may beof an independent power domain and can be configured to enter and exitactive states and/or maximum performance states based on workload. Oneor more cores 210 may be heterogeneous to the other cores, e.g., havingdifferent micro-architectures, instruction set architectures, pipelinedepths, power and performance capabilities. The various cores may becoupled via an interconnect 215 to a system agent or uncore 220 thatincludes various components. As seen, the uncore 220 may include ashared cache 230 which may be a last level cache. In addition, theuncore may include an integrated memory controller 240 to communicatewith a system memory (not shown in FIG. 2 ), e.g., via a memory bus.Uncore 220 also includes various interfaces 250 and a power control unit255, which may include logic to perform power management techniques,including the loose lock-step power management control as describedherein. To this end, PCU 255 may include a synchronization circuit 256that is configured to identify multiple cores or other processingcircuits to be collected into a given synchronization domain and controloperating points of these collected circuits to enable dynamic looselock-step operation.

In addition, by interfaces 250 a-250 n, connection can be made tovarious off-chip components such as peripheral devices, mass storage andso forth. While shown with this particular implementation in theembodiment of FIG. 2 , the scope of the present invention is not limitedin this regard.

Referring now to FIG. 3 , shown is a block diagram of a multi-domainprocessor in accordance with another embodiment of the presentinvention. As shown in the embodiment of FIG. 3 , processor 300 includesmultiple domains. Specifically, a core domain 310 can include aplurality of cores 310 a-310 n, a graphics domain 320 can include one ormore graphics engines, and a system agent domain 350 may further bepresent. In some embodiments, system agent domain 350 may execute at anindependent frequency than the core domain and may remain powered on atall times to handle power control events and power management such thatdomains 310 and 320 can be controlled to dynamically enter into and exithigh power and low power states. Each of domains 310 and 320 may operateat different voltage and/or power. Note that while only shown with threedomains, understand the scope of the present invention is not limited inthis regard and additional domains can be present in other embodiments.For example, multiple core domains may be present each including atleast one core.

In general, each core 310 may further include low level caches inaddition to various execution units and additional processing elements.In turn, the various cores may be coupled to each other and to a sharedcache memory formed of a plurality of units of a last level cache (LLC)340 a-340 n. In various embodiments, LLC 340 may be shared amongst thecores and the graphics engine, as well as various media processingcircuitry. As seen, a ring interconnect 330 thus couples the corestogether, and provides interconnection between the cores, graphicsdomain 320 and system agent circuitry 350. In one embodiment,interconnect 330 can be part of the core domain. However in otherembodiments the ring interconnect can be of its own domain.

As further seen, system agent domain 350 may include display controller352 which may provide control of and an interface to an associateddisplay. As further seen, system agent domain 350 may include a powercontrol unit 355 which can include logic to perform power managementtechniques, including dynamic loose lock-step control techniquesdescribed herein. To this end, PCU 355 includes a synchronizationcircuit 356 that is configured to identify multiple cores and/or otherprocessing circuits to enter into a synchronization domain and becontrolled to operate in a loose lock-step manner as described herein.

As further seen in FIG. 3 , processor 300 can further include anintegrated memory controller (IMC) 370 that can provide for an interfaceto a system memory, such as a dynamic random access memory (DRAM).Multiple interfaces 380 a-380 n may be present to enable interconnectionbetween the processor and other circuitry. For example, in oneembodiment at least one direct media interface (DMI) interface may beprovided as well as one or more PCIe™ interfaces. Still further, toprovide for communications between other agents such as additionalprocessors or other circuitry, one or more QPI interfaces may also beprovided. Although shown at this high level in the embodiment of FIG. 3, understand the scope of the present invention is not limited in thisregard.

Referring to FIG. 4 , an embodiment of a processor including multiplecores is illustrated. Processor 400 includes any processor or processingdevice, such as a microprocessor, an embedded processor, a digitalsignal processor (DSP), a network processor, a handheld processor, anapplication processor, a co-processor, a system on a chip (SoC), orother device to execute code. Processor 400, in one embodiment, includesat least two cores—cores 401 and 402, which may include asymmetric coresor symmetric cores (the illustrated embodiment). However, processor 400may include any number of processing elements that may be symmetric orasymmetric.

In one embodiment, a processing element refers to hardware or logic tosupport a software thread. Examples of hardware processing elementsinclude: a thread unit, a thread slot, a thread, a process unit, acontext, a context unit, a logical processor, a hardware thread, a core,and/or any other element, which is capable of holding a state for aprocessor, such as an execution state or architectural state. In otherwords, a processing element, in one embodiment, refers to any hardwarecapable of being independently associated with code, such as a softwarethread, operating system, application, or other code. A physicalprocessor typically refers to an integrated circuit, which potentiallyincludes any number of other processing elements, such as cores orhardware threads.

A core often refers to logic located on an integrated circuit capable ofmaintaining an independent architectural state, wherein eachindependently maintained architectural state is associated with at leastsome dedicated execution resources. In contrast to cores, a hardwarethread typically refers to any logic located on an integrated circuitcapable of maintaining an independent architectural state, wherein theindependently maintained architectural states share access to executionresources. As can be seen, when certain resources are shared and othersare dedicated to an architectural state, the line between thenomenclature of a hardware thread and core overlaps. Yet often, a coreand a hardware thread are viewed by an operating system as individuallogical processors, where the operating system is able to individuallyschedule operations on each logical processor.

Physical processor 400, as illustrated in FIG. 4 , includes two cores,cores 401 and 402. Here, cores 401 and 402 are considered symmetriccores, i.e., cores with the same configurations, functional units,and/or logic. In another embodiment, core 401 includes an out-of-orderprocessor core, while core 402 includes an in-order processor core.However, cores 401 and 402 may be individually selected from any type ofcore, such as a native core, a software managed core, a core adapted toexecute a native instruction set architecture (ISA), a core adapted toexecute a translated ISA, a co-designed core, or other known core. Yetto further the discussion, the functional units illustrated in core 401are described in further detail below, as the units in core 402 operatein a similar manner.

As depicted, core 401 includes two hardware threads 401 a and 401 b,which may also be referred to as hardware thread slots 401 a and 401 b.Therefore, software entities, such as an operating system, in oneembodiment potentially view processor 400 as four separate processors,i.e., four logical processors or processing elements capable ofexecuting four software threads concurrently. As alluded to above, afirst thread is associated with architecture state registers 401 a, asecond thread is associated with architecture state registers 401 b, athird thread may be associated with architecture state registers 402 a,and a fourth thread may be associated with architecture state registers402 b. Here, each of the architecture state registers (401 a, 401 b, 402a, and 402 b) may be referred to as processing elements, thread slots,or thread units, as described above. As illustrated, architecture stateregisters 401 a are replicated in architecture state registers 401 b, soindividual architecture states/contexts are capable of being stored forlogical processor 401 a and logical processor 401 b. In core 401, othersmaller resources, such as instruction pointers and renaming logic inallocator and renamer block 430 may also be replicated for threads 401 aand 401 b. Some resources, such as re-order buffers inreorder/retirement unit 435, branch target buffer and instructiontranslation lookaside buffer (BTB and I-TLB) 420, load/store buffers,and queues may be shared through partitioning. Other resources, such asgeneral purpose internal registers, page-table base register(s),low-level data-cache and data-TLB 450, execution unit(s) 440, andportions of out-of-order unit 435 are potentially fully shared.

Processor 400 often includes other resources, which may be fully shared,shared through partitioning, or dedicated by/to processing elements. InFIG. 4 , an embodiment of a purely exemplary processor with illustrativelogical units/resources of a processor is illustrated. Note that aprocessor may include, or omit, any of these functional units, as wellas include any other known functional units, logic, or firmware notdepicted. As illustrated, core 401 includes a simplified, representativeout-of-order (OOO) processor core. But an in-order processor may beutilized in different embodiments. The OOO core includes a branch targetbuffer 420 to predict branches to be executed/taken and aninstruction-translation buffer (I-TLB) 420 to store address translationentries for instructions.

Core 401 further includes decode module 425 coupled to a fetch unit todecode fetched elements. Fetch logic, in one embodiment, includesindividual sequencers associated with thread slots 401 a, 401 b,respectively. Usually core 401 is associated with a first ISA, whichdefines/specifies instructions executable on processor 400. Oftenmachine code instructions that are part of the first ISA include aportion of the instruction (referred to as an opcode), whichreferences/specifies an instruction or operation to be performed. Decodelogic 425 includes circuitry that recognizes these instructions fromtheir opcodes and passes the decoded instructions on in the pipeline forprocessing as defined by the first ISA. For example, decoders 425, inone embodiment, include logic designed or adapted to recognize specificinstructions, such as transactional instruction. As a result of therecognition by decoders 425, the architecture or core 401 takesspecific, predefined actions to perform tasks associated with theappropriate instruction. It is important to note that any of the tasks,blocks, operations, and methods described herein may be performed inresponse to a single or multiple instructions; some of which may be newor old instructions.

In one example, allocator and renamer block 430 includes an allocator toreserve resources, such as register files to store instructionprocessing results. However, threads 401 a and 401 b are potentiallycapable of out-of-order execution, where allocator and renamer block 430also reserves other resources, such as reorder buffers to trackinstruction results. Unit 430 may also include a register renamer torename program/instruction reference registers to other registersinternal to processor 400. Reorder/retirement unit 435 includescomponents, such as the reorder buffers mentioned above, load buffers,and store buffers, to support out-of-order execution and later in-orderretirement of instructions executed out-of-order.

Scheduler and execution unit(s) block 440, in one embodiment, includes ascheduler unit to schedule instructions/operation on execution units.For example, a floating point instruction is scheduled on a port of anexecution unit that has an available floating point execution unit.Register files associated with the execution units are also included tostore information instruction processing results. Exemplary executionunits include a floating point execution unit, an integer executionunit, a jump execution unit, a load execution unit, a store executionunit, and other known execution units.

Lower level data cache and data translation lookaside buffer (D-TLB) 450are coupled to execution unit(s) 440. The data cache is to storerecently used/operated on elements, such as data operands, which arepotentially held in memory coherency states. The D-TLB is to storerecent virtual/linear to physical address translations. As a specificexample, a processor may include a page table structure to breakphysical memory into a plurality of virtual pages.

Here, cores 401 and 402 share access to higher-level or further-outcache 410, which is to cache recently fetched elements. Note thathigher-level or further-out refers to cache levels increasing or gettingfurther away from the execution unit(s). In one embodiment, higher-levelcache 410 is a last-level data cache—last cache in the memory hierarchyon processor 400—such as a second or third level data cache. However,higher level cache 410 is not so limited, as it may be associated withor includes an instruction cache. A trace cache—a type of instructioncache—instead may be coupled after decoder 425 to store recently decodedtraces.

In the depicted configuration, processor 400 also includes bus interfacemodule 405 and a power control unit 460, which may perform powermanagement in accordance with an embodiment of the present invention. Inthis scenario, bus interface 405 is to communicate with devices externalto processor 400, such as system memory and other components.

A memory controller 470 may interface with other devices such as one ormany memories. In an example, bus interface 405 includes a ringinterconnect with a memory controller for interfacing with a memory anda graphics controller for interfacing with a graphics processor. In anSoC environment, even more devices, such as a network interface,coprocessors, memory, graphics processor, and any other known computerdevices/interface may be integrated on a single die or integratedcircuit to provide small form factor with high functionality and lowpower consumption.

Referring now to FIG. 5 , shown is a block diagram of amicro-architecture of a processor core in accordance with one embodimentof the present invention. As shown in FIG. 5 , processor core 500 may bea multi-stage pipelined out-of-order processor. Core 500 may operate atvarious voltages based on a received operating voltage, which may bereceived from an integrated voltage regulator or external voltageregulator.

As seen in FIG. 5 , core 500 includes front end units 510, which may beused to fetch instructions to be executed and prepare them for use laterin the processor pipeline. For example, front end units 510 may includea fetch unit 501, an instruction cache 503, and an instruction decoder505. In some implementations, front end units 510 may further include atrace cache, along with microcode storage as well as a micro-operationstorage. Fetch unit 501 may fetch macro-instructions, e.g., from memoryor instruction cache 503, and feed them to instruction decoder 505 todecode them into primitives, i.e., micro-operations for execution by theprocessor.

Coupled between front end units 510 and execution units 520 is anout-of-order (OOO) engine 515 that may be used to receive themicro-instructions and prepare them for execution. More specifically OOOengine 515 may include various buffers to re-order micro-instructionflow and allocate various resources needed for execution, as well as toprovide renaming of logical registers onto storage locations withinvarious register files such as register file 530 and extended registerfile 535. Register file 530 may include separate register files forinteger and floating point operations. For purposes of configuration,control, and additional operations, a set of machine specific registers(MSRs) 538 may also be present and accessible to various logic withincore 500 (and external to the core).

Various resources may be present in execution units 520, including, forexample, various integer, floating point, and single instructionmultiple data (SIMD) logic units, among other specialized hardware. Forexample, such execution units may include one or more arithmetic logicunits (ALUs) 522 and one or more vector execution units 524, among othersuch execution units.

Results from the execution units may be provided to retirement logic,namely a reorder buffer (ROB) 540. More specifically, ROB 540 mayinclude various arrays and logic to receive information associated withinstructions that are executed. This information is then examined by ROB540 to determine whether the instructions can be validly retired andresult data committed to the architectural state of the processor, orwhether one or more exceptions occurred that prevent a proper retirementof the instructions. Of course, ROB 540 may handle other operationsassociated with retirement.

As shown in FIG. 5 , ROB 540 is coupled to a cache 550 which, in oneembodiment may be a low level cache (e.g., an L1 cache) although thescope of the present invention is not limited in this regard. Also,execution units 520 can be directly coupled to cache 550. From cache550, data communication may occur with higher level caches, systemmemory and so forth. While shown with this high level in the embodimentof FIG. 5 , understand the scope of the present invention is not limitedin this regard. For example, while the implementation of FIG. 5 is withregard to an out-of-order machine such as of an Intel® x86 instructionset architecture (ISA), the scope of the present invention is notlimited in this regard. That is, other embodiments may be implemented inan in-order processor, a reduced instruction set computing (RISC)processor such as an ARM-based processor, or a processor of another typeof ISA that can emulate instructions and operations of a different ISAvia an emulation engine and associated logic circuitry.

Referring now to FIG. 6 , shown is a block diagram of amicro-architecture of a processor core in accordance with anotherembodiment. In the embodiment of FIG. 6 , core 600 may be a low powercore of a different micro-architecture, such as an Intel® Atom™-basedprocessor having a relatively limited pipeline depth designed to reducepower consumption. As seen, core 600 includes an instruction cache 610coupled to provide instructions to an instruction decoder 615. A branchpredictor 605 may be coupled to instruction cache 610. Note thatinstruction cache 610 may further be coupled to another level of a cachememory, such as an L2 cache (not shown for ease of illustration in FIG.6 ). In turn, instruction decoder 615 provides decoded instructions toan issue queue (IQ) 620 for storage and delivery to a given executionpipeline. A microcode ROM 618 is coupled to instruction decoder 615.

A floating point pipeline 630 includes a floating point (FP) registerfile 632 which may include a plurality of architectural registers of agiven bit width such as 128, 256 or 512 bits. Pipeline 630 includes afloating point scheduler 634 to schedule instructions for execution onone of multiple execution units of the pipeline. In the embodimentshown, such execution units include an ALU 635, a shuffle unit 636, anda floating point adder 638. In turn, results generated in theseexecution units may be provided back to buffers and/or registers ofregister file 632. Of course understand while shown with these fewexample execution units, additional or different floating pointexecution units may be present in another embodiment.

An integer pipeline 640 also may be provided. In the embodiment shown,pipeline 640 includes an integer (INT) register file 642 which mayinclude a plurality of architectural registers of a given bit width suchas 128 or 256 bits. Pipeline 640 includes an integer execution (IE)scheduler 644 to schedule instructions for execution on one of multipleexecution units of the pipeline. In the embodiment shown, such executionunits include an ALU 645, a shifter unit 646, and a jump execution unit(JEU) 648. In turn, results generated in these execution units may beprovided back to buffers and/or registers of register file 642. Ofcourse understand while shown with these few example execution units,additional or different integer execution units may be present inanother embodiment.

A memory execution (ME) scheduler 650 may schedule memory operations forexecution in an address generation unit (AGU) 652, which is also coupledto a TLB 654. As seen, these structures may couple to a data cache 660,which may be a L0 and/or L1 data cache that in turn couples toadditional levels of a cache memory hierarchy, including an L2 cachememory.

To provide support for out-of-order execution, an allocator/renamer 670may be provided, in addition to a reorder buffer 680, which isconfigured to reorder instructions executed out of order for retirementin order. Although shown with this particular pipeline architecture inthe illustration of FIG. 6 , understand that many variations andalternatives are possible.

Note that in a processor having asymmetric cores, such as in accordancewith the micro-architectures of FIGS. 5 and 6 , workloads may bedynamically swapped between the cores for power management reasons, asthese cores, although having different pipeline designs and depths, maybe of the same or related ISA. Such dynamic core swapping may beperformed in a manner transparent to a user application (and possiblykernel also).

Referring to FIG. 7 , shown is a block diagram of a micro-architectureof a processor core in accordance with yet another embodiment. Asillustrated in FIG. 7 , a core 700 may include a multi-staged in-orderpipeline to execute at very low power consumption levels. As one suchexample, processor 700 may have a micro-architecture in accordance withan ARM Cortex A53 design available from ARM Holdings, LTD., Sunnyvale,Calif. In an implementation, an 8-stage pipeline may be provided that isconfigured to execute both 32-bit and 64-bit code. Core 700 includes afetch unit 710 that is configured to fetch instructions and provide themto a decode unit 715, which may decode the instructions, e.g.,macro-instructions of a given ISA such as an ARMv8 ISA. Note furtherthat a queue 730 may couple to decode unit 715 to store decodedinstructions. Decoded instructions are provided to an issue logic 725,where the decoded instructions may be issued to a given one of multipleexecution units.

With further reference to FIG. 7 , issue logic 725 may issueinstructions to one of multiple execution units. In the embodimentshown, these execution units include an integer unit 735, a multiplyunit 740, a floating point/vector unit 750, a dual issue unit 760, and aload/store unit 770. The results of these different execution units maybe provided to a writeback (WB) unit 780. Understand that while a singlewriteback unit is shown for ease of illustration, in someimplementations separate writeback units may be associated with each ofthe execution units. Furthermore, understand that while each of theunits and logic shown in FIG. 7 is represented at a high level, aparticular implementation may include more or different structures. Aprocessor designed using one or more cores having a pipeline as in FIG.7 may be implemented in many different end products, extending frommobile devices to server systems.

Referring to FIG. 8 , shown is a block diagram of a micro-architectureof a processor core in accordance with a still further embodiment. Asillustrated in FIG. 8 , a core 800 may include a multi-stage multi-issueout-of-order pipeline to execute at very high performance levels (whichmay occur at higher power consumption levels than core 700 of FIG. 7 ).As one such example, processor 800 may have a microarchitecture inaccordance with an ARM Cortex A57 design. In an implementation, a 15 (orgreater)-stage pipeline may be provided that is configured to executeboth 32-bit and 64-bit code. In addition, the pipeline may provide for 3(or greater)-wide and 3 (or greater)-issue operation. Core 800 includesa fetch unit 810 that is configured to fetch instructions and providethem to a decoder/renamer/dispatcher unit 815 coupled to a cache 820.Unit 815 may decode the instructions, e.g., macro-instructions of anARMv8 instruction set architecture, rename register references withinthe instructions, and dispatch the instructions (eventually) to aselected execution unit. Decoded instructions may be stored in a queue825. Note that while a single queue structure is shown for ease ofillustration in FIG. 8 , understand that separate queues may be providedfor each of the multiple different types of execution units.

Also shown in FIG. 8 is an issue logic 830 from which decodedinstructions stored in queue 825 may be issued to a selected executionunit. Issue logic 830 also may be implemented in a particular embodimentwith a separate issue logic for each of the multiple different types ofexecution units to which issue logic 830 couples.

Decoded instructions may be issued to a given one of multiple executionunits. In the embodiment shown, these execution units include one ormore integer units 835, a multiply unit 840, a floating point/vectorunit 850, a branch unit 860, and a load/store unit 870. In anembodiment, floating point/vector unit 850 may be configured to handleSIMD or vector data of 128 or 256 bits. Still further, floatingpoint/vector execution unit 850 may perform IEEE-754 double precisionfloating-point operations. The results of these different executionunits may be provided to a writeback unit 880. Note that in someimplementations separate writeback units may be associated with each ofthe execution units. Furthermore, understand that while each of theunits and logic shown in FIG. 8 is represented at a high level, aparticular implementation may include more or different structures.

Note that in a processor having asymmetric cores, such as in accordancewith the micro-architectures of FIGS. 7 and 8 , workloads may bedynamically swapped for power management reasons, as these cores,although having different pipeline designs and depths, may be of thesame or related ISA. Such dynamic core swapping may be performed in amanner transparent to a user application (and possibly kernel also).

A processor designed using one or more cores having pipelines as in anyone or more of FIGS. 5-8 may be implemented in many different endproducts, extending from mobile devices to server systems. Referring nowto FIG. 9 , shown is a block diagram of a processor in accordance withanother embodiment of the present invention. In the embodiment of FIG. 9, processor 900 may be a SoC including multiple domains, each of whichmay be controlled to operate at an independent operating voltage andoperating frequency. As a specific illustrative example, processor 900may be an Intel® Architecture Core™-based processor such as an i3, i5,i7 or another such processor available from Intel Corporation. However,other low power processors such as available from Advanced MicroDevices, Inc. (AMD) of Sunnyvale, Calif., an ARM-based design from ARMHoldings, Ltd. or licensee thereof or a MIPS-based design from MIPSTechnologies, Inc. of Sunnyvale, Calif., or their licensees or adoptersmay instead be present in other embodiments such as an Apple A7processor, a Qualcomm Snapdragon processor, or Texas Instruments OMAPprocessor. Such SoC may be used in a low power system such as asmartphone, tablet computer, phablet computer, Ultrabook™ computer orother portable computing device, which may incorporate a heterogeneoussystem architecture having a heterogeneous system architecture-basedprocessor design.

In the high level view shown in FIG. 9 , processor 900 includes aplurality of core units 910 a-910 n. Each core unit may include one ormore processor cores, one or more cache memories and other circuitry.Each core unit 910 may support one or more instruction sets (e.g., anx86 instruction set (with some extensions that have been added withnewer versions); a MIPS instruction set; an ARM instruction set (withoptional additional extensions such as NEON)) or other instruction setor combinations thereof. Note that some of the core units may beheterogeneous resources (e.g., of a different design). In addition, eachsuch core may be coupled to a cache memory (not shown) which in anembodiment may be a shared level two (L2) cache memory. A non-volatilestorage 930 may be used to store various program and other data. Forexample, this storage may be used to store at least portions ofmicrocode, boot information such as a BIOS, other system software or soforth.

Each core unit 910 may also include an interface such as a bus interfaceunit to enable interconnection to additional circuitry of the processor.In an embodiment, each core unit 910 couples to a coherent fabric thatmay act as a primary cache coherent on-die interconnect that in turncouples to a memory controller 935. In turn, memory controller 935controls communications with a memory such as a DRAM (not shown for easeof illustration in FIG. 9 ).

In addition to core units, additional processing engines are presentwithin the processor, including at least one graphics unit 920 which mayinclude one or more graphics processing units (GPUs) to perform graphicsprocessing as well as to possibly execute general purpose operations onthe graphics processor (so-called GPGPU operation). In addition, atleast one image signal processor 925 may be present. Signal processor925 may be configured to process incoming image data received from oneor more capture devices, either internal to the SoC or off-chip.

Other accelerators also may be present. In the illustration of FIG. 9 ,a video coder 950 may perform coding operations including encoding anddecoding for video information, e.g., providing hardware accelerationsupport for high definition video content. A display controller 955further may be provided to accelerate display operations includingproviding support for internal and external displays of a system. Inaddition, a security processor 945 may be present to perform securityoperations such as secure boot operations, various cryptographyoperations and so forth.

Each of the units may have its power consumption controlled via a powermanager 940, which may include control logic to perform the variouspower management techniques described herein.

In some embodiments, SoC 900 may further include a non-coherent fabriccoupled to the coherent fabric to which various peripheral devices maycouple. One or more interfaces 960 a-960 d enable communication with oneor more off-chip devices. Such communications may be via a variety ofcommunication protocols such as PCIe™, GPIO, USB, I²C, UART, MIPI, SDIO,DDR, SPI, HDMI, among other types of communication protocols. Althoughshown at this high level in the embodiment of FIG. 9 , understand thescope of the present invention is not limited in this regard.

Referring now to FIG. 10 , shown is a block diagram of a representativeSoC. In the embodiment shown, SoC 1000 may be a multi-core SoCconfigured for low power operation to be optimized for incorporationinto a smartphone or other low power device such as a tablet computer orother portable computing device. As an example, SoC 1000 may beimplemented using asymmetric or different types of cores, such ascombinations of higher power and/or low power cores, e.g., out-of-ordercores and in-order cores. In different embodiments, these cores may bebased on an Intel® Architecture™ core design or an ARM architecturedesign. In yet other embodiments, a mix of Intel and ARM cores may beimplemented in a given SoC.

As seen in FIG. 10 , SoC 1000 includes a first core domain 1010 having aplurality of first cores 1012 a-1012 d. In an example, these cores maybe low power cores such as in-order cores. In one embodiment these firstcores may be implemented as ARM Cortex A53 cores. In turn, these corescouple to a cache memory 1015 of core domain 1010. In addition, SoC 1000includes a second core domain 1020. In the illustration of FIG. 10 ,second core domain 1020 has a plurality of second cores 1022 a-1022 d.In an example, these cores may be higher power-consuming cores thanfirst cores 1012. In an embodiment, the second cores may be out-of-ordercores, which may be implemented as ARM Cortex A57 cores. In turn, thesecores couple to a cache memory 1025 of core domain 1020. Note that whilethe example shown in FIG. 10 includes 4 cores in each domain, understandthat more or fewer cores may be present in a given domain in otherexamples.

With further reference to FIG. 10 , a graphics domain 1030 also isprovided, which may include one or more graphics processing units (GPUs)configured to independently execute graphics workloads, e.g., providedby one or more cores of core domains 1010 and 1020. As an example, GPUdomain 1030 may be used to provide display support for a variety ofscreen sizes, in addition to providing graphics and display renderingoperations.

As seen, the various domains couple to a coherent interconnect 1040,which in an embodiment may be a cache coherent interconnect fabric thatin turn couples to an integrated memory controller 1050. Coherentinterconnect 1040 may include a shared cache memory, such as an L3cache, in some examples. In an embodiment, memory controller 1050 may bea direct memory controller to provide for multiple channels ofcommunication with an off-chip memory, such as multiple channels of aDRAM (not shown for ease of illustration in FIG. 10 ).

In different examples, the number of the core domains may vary. Forexample, for a low power SoC suitable for incorporation into a mobilecomputing device, a limited number of core domains such as shown in FIG.10 may be present. Still further, in such low power SoCs, core domain1020 including higher power cores may have fewer numbers of such cores.For example, in one implementation two cores 1022 may be provided toenable operation at reduced power consumption levels. In addition, thedifferent core domains may also be coupled to an interrupt controller toenable dynamic swapping of workloads between the different domains.

In yet other embodiments, a greater number of core domains, as well asadditional optional IP logic may be present, in that an SoC can bescaled to higher performance (and power) levels for incorporation intoother computing devices, such as desktops, servers, high performancecomputing systems, base stations forth. As one such example, 4 coredomains each having a given number of out-of-order cores may beprovided. Still further, in addition to optional GPU support (which asan example may take the form of a GPGPU), one or more accelerators toprovide optimized hardware support for particular functions (e.g. webserving, network processing, switching or so forth) also may beprovided. In addition, an input/output interface may be present tocouple such accelerators to off-chip components.

Referring now to FIG. 11 , shown is a block diagram of another exampleSoC. In the embodiment of FIG. 11 , SoC 1100 may include variouscircuitry to enable high performance for multimedia applications,communications and other functions. As such, SoC 1100 is suitable forincorporation into a wide variety of portable and other devices, such assmartphones, tablet computers, smart TVs and so forth. In the exampleshown, SoC 1100 includes a central processor unit (CPU) domain 1110. Inan embodiment, a plurality of individual processor cores may be presentin CPU domain 1110. As one example, CPU domain 1110 may be a quad coreprocessor having 4 multithreaded cores. Such processors may behomogeneous or heterogeneous processors, e.g., a mix of low power andhigh power processor cores.

In turn, a GPU domain 1120 is provided to perform advanced graphicsprocessing in one or more GPUs to handle graphics and compute APIs. ADSP unit 1130 may provide one or more low power DSPs for handlinglow-power multimedia applications such as music playback, audio/videoand so forth, in addition to advanced calculations that may occur duringexecution of multimedia instructions. In turn, a communication unit 1140may include various components to provide connectivity via variouswireless protocols, such as cellular communications (including 3G/4GLTE), wireless local area protocols such as Bluetooth™, IEEE 802.11, andso forth.

Still further, a multimedia processor 1150 may be used to performcapture and playback of high definition video and audio content,including processing of user gestures. A sensor unit 1160 may include aplurality of sensors and/or a sensor controller to interface to variousoff-chip sensors present in a given platform. An image signal processor1170 may be provided with one or more separate ISPs to perform imageprocessing with regard to captured content from one or more cameras of aplatform, including still and video cameras.

A display processor 1180 may provide support for connection to a highdefinition display of a given pixel density, including the ability towirelessly communicate content for playback on such display. Stillfurther, a location unit 1190 may include a GPS receiver with supportfor multiple GPS constellations to provide applications highly accuratepositioning information obtained using as such GPS receiver. Understandthat while shown with this particular set of components in the exampleof FIG. 11 , many variations and alternatives are possible.

Referring now to FIG. 12 , shown is a block diagram of an example systemwith which embodiments can be used. As seen, system 1200 may be asmartphone or other wireless communicator. A baseband processor 1205 isconfigured to perform various signal processing with regard tocommunication signals to be transmitted from or received by the system.In turn, baseband processor 1205 is coupled to an application processor1210, which may be a main CPU of the system to execute an OS and othersystem software, in addition to user applications such as manywell-known social media and multimedia apps. Application processor 1210may further be configured to perform a variety of other computingoperations for the device.

In turn, application processor 1210 can couple to a userinterface/display 1220, e.g., a touch screen display. In addition,application processor 1210 may couple to a memory system including anon-volatile memory, namely a flash memory 1230 and a system memory,namely a dynamic random access memory (DRAM) 1235. As further seen,application processor 1210 further couples to a capture device 1240 suchas one or more image capture devices that can record video and/or stillimages.

Still referring to FIG. 12 , a universal integrated circuit card (UICC)1240 comprising a subscriber identity module and possibly a securestorage and cryptoprocessor is also coupled to application processor1210. System 1200 may further include a security processor 1250 that maycouple to application processor 1210. A plurality of sensors 1225 maycouple to application processor 1210 to enable input of a variety ofsensed information such as accelerometer and other environmentalinformation. An audio output device 1295 may provide an interface tooutput sound, e.g., in the form of voice communications, played orstreaming audio data and so forth.

As further illustrated, a near field communication (NFC) contactlessinterface 1260 is provided that communicates in a NFC near field via anNFC antenna 1265. While separate antennae are shown in FIG. 12 ,understand that in some implementations one antenna or a different setof antennae may be provided to enable various wireless functionality.

A power management integrated circuit (PMIC) 1215 couples to applicationprocessor 1210 to perform platform level power management. To this end,PMIC 1215 may issue power management requests to application processor1210 to enter certain low power states as desired. Furthermore, based onplatform constraints, PMIC 1215 may also control the power level ofother components of system 1200.

To enable communications to be transmitted and received, variouscircuitry may be coupled between baseband processor 1205 and an antenna1290. Specifically, a radio frequency (RF) transceiver 1270 and awireless local area network (WLAN) transceiver 1275 may be present. Ingeneral, RF transceiver 1270 may be used to receive and transmitwireless data and calls according to a given wireless communicationprotocol such as 3G or 4G wireless communication protocol such as inaccordance with a code division multiple access (CDMA), global systemfor mobile communication (GSM), long term evolution (LTE) or otherprotocol. In addition a GPS sensor 1280 may be present. Other wirelesscommunications such as receipt or transmission of radio signals, e.g.,AM/FM and other signals may also be provided. In addition, via WLANtransceiver 1275, local wireless communications can also be realized.

Referring now to FIG. 13 , shown is a block diagram of another examplesystem with which embodiments may be used. In the illustration of FIG.13 , system 1300 may be mobile low-power system such as a tabletcomputer, 2:1 tablet, phablet or other convertible or standalone tabletsystem. As illustrated, a SoC 1310 is present and may be configured tooperate as an application processor for the device.

A variety of devices may couple to SoC 1310. In the illustration shown,a memory subsystem includes a flash memory 1340 and a DRAM 1345 coupledto SoC 1310. In addition, a touch panel 1320 is coupled to the SoC 1310to provide display capability and user input via touch, includingprovision of a virtual keyboard on a display of touch panel 1320. Toprovide wired network connectivity, SoC 1310 couples to an Ethernetinterface 1330. A peripheral hub 1325 is coupled to SoC 1310 to enableinterfacing with various peripheral devices, such as may be coupled tosystem 1300 by any of various ports or other connectors.

In addition to internal power management circuitry and functionalitywithin SoC 1310, a PMIC 1380 is coupled to SoC 1310 to provideplatform-based power management, e.g., based on whether the system ispowered by a battery 1390 or AC power via an AC adapter 1395. Inaddition to this power source-based power management, PMIC 1380 mayfurther perform platform power management activities based onenvironmental and usage conditions. Still further, PMIC 1380 maycommunicate control and status information to SoC 1310 to cause variouspower management actions within SoC 1310.

Still referring to FIG. 13 , to provide for wireless capabilities, aWLAN unit 1350 is coupled to SoC 1310 and in turn to an antenna 1355. Invarious implementations, WLAN unit 1350 may provide for communicationaccording to one or more wireless protocols.

As further illustrated, a plurality of sensors 1360 may couple to SoC1310. These sensors may include various accelerometer, environmental andother sensors, including user gesture sensors. Finally, an audio codec1365 is coupled to SoC 1310 to provide an interface to an audio outputdevice 1370. Of course understand that while shown with this particularimplementation in FIG. 13 , many variations and alternatives arepossible.

Referring now to FIG. 14 , shown is a block diagram of a representativecomputer system such as notebook, Ultrabook™ or other small form factorsystem. A processor 1410, in one embodiment, includes a microprocessor,multi-core processor, multithreaded processor, an ultra low voltageprocessor, an embedded processor, or other known processing element. Inthe illustrated implementation, processor 1410 acts as a main processingunit and central hub for communication with many of the variouscomponents of the system 1400, and may include power managementcircuitry as described herein. As one example, processor 1410 isimplemented as a SoC.

Processor 1410, in one embodiment, communicates with a system memory1415. As an illustrative example, the system memory 1415 is implementedvia multiple memory devices or modules to provide for a given amount ofsystem memory.

To provide for persistent storage of information such as data,applications, one or more operating systems and so forth, a mass storage1420 may also couple to processor 1410. In various embodiments, toenable a thinner and lighter system design as well as to improve systemresponsiveness, this mass storage may be implemented via a SSD or themass storage may primarily be implemented using a hard disk drive (HDD)with a smaller amount of SSD storage to act as a SSD cache to enablenon-volatile storage of context state and other such information duringpower down events so that a fast power up can occur on re-initiation ofsystem activities. Also shown in FIG. 14 , a flash device 1422 may becoupled to processor 1410, e.g., via a serial peripheral interface(SPI). This flash device may provide for non-volatile storage of systemsoftware, including a basic input/output software (BIOS) as well asother firmware of the system.

Various input/output (I/O) devices may be present within system 1400.Specifically shown in the embodiment of FIG. 14 is a display 1424 whichmay be a high definition LCD or LED panel that further provides for atouch screen 1425. In one embodiment, display 1424 may be coupled toprocessor 1410 via a display interconnect that can be implemented as ahigh performance graphics interconnect. Touch screen 1425 may be coupledto processor 1410 via another interconnect, which in an embodiment canbe an I²C interconnect. As further shown in FIG. 14 , in addition totouch screen 1425, user input by way of touch can also occur via a touchpad 1430 which may be configured within the chassis and may also becoupled to the same I²C interconnect as touch screen 1425.

For perceptual computing and other purposes, various sensors may bepresent within the system and may be coupled to processor 1410 indifferent manners. Certain inertial and environmental sensors may coupleto processor 1410 through a sensor hub 1440, e.g., via an I²Cinterconnect. In the embodiment shown in FIG. 14 , these sensors mayinclude an accelerometer 1441, an ambient light sensor (ALS) 1442, acompass 1443 and a gyroscope 1444. Other environmental sensors mayinclude one or more thermal sensors 1446 which in some embodimentscouple to processor 1410 via a system management bus (SMBus) bus.

Also seen in FIG. 14 , various peripheral devices may couple toprocessor 1410 via a low pin count (LPC) interconnect. In the embodimentshown, various components can be coupled through an embedded controller1435. Such components can include a keyboard 1436 (e.g., coupled via aPS2 interface), a fan 1437, and a thermal sensor 1439. In someembodiments, touch pad 1430 may also couple to EC 1435 via a PS2interface. In addition, a security processor such as a trusted platformmodule (TPM) 1438 may also couple to processor 1410 via this LPCinterconnect.

System 1400 can communicate with external devices in a variety ofmanners, including wirelessly. In the embodiment shown in FIG. 14 ,various wireless modules, each of which can correspond to a radioconfigured for a particular wireless communication protocol, arepresent. One manner for wireless communication in a short range such asa near field may be via a NFC unit 1445 which may communicate, in oneembodiment with processor 1410 via an SMBus. Note that via this NFC unit1445, devices in close proximity to each other can communicate.

As further seen in FIG. 14 , additional wireless units can include othershort range wireless engines including a WLAN unit 1450 and a Bluetooth™unit 1452. Using WLAN unit 1450, Wi-Fi™ communications can be realized,while via Bluetooth™ unit 1452, short range Bluetooth™ communicationscan occur. These units may communicate with processor 1410 via a givenlink.

In addition, wireless wide area communications, e.g., according to acellular or other wireless wide area protocol, can occur via a WWAN unit1456 which in turn may couple to a subscriber identity module (SIM)1457. In addition, to enable receipt and use of location information, aGPS module 1455 may also be present. Note that in the embodiment shownin FIG. 14 , WWAN unit 1456 and an integrated capture device such as acamera module 1454 may communicate via a given link.

To provide for audio inputs and outputs, an audio processor can beimplemented via a digital signal processor (DSP) 1460, which may coupleto processor 1410 via a high definition audio (HDA) link. Similarly, DSP1460 may communicate with an integrated coder/decoder (CODEC) andamplifier 1462 that in turn may couple to output speakers 1463 which maybe implemented within the chassis. Similarly, amplifier and CODEC 1462can be coupled to receive audio inputs from a microphone 1465 which inan embodiment can be implemented via dual array microphones (such as adigital microphone array) to provide for high quality audio inputs toenable voice-activated control of various operations within the system.Note also that audio outputs can be provided from amplifier/CODEC 1462to a headphone jack 1464. Although shown with these particularcomponents in the embodiment of FIG. 14 , understand the scope of thepresent invention is not limited in this regard.

Embodiments may be implemented in many different system types. Referringnow to FIG. 15 , shown is a block diagram of a system in accordance withan embodiment of the present invention. As shown in FIG. 15 ,multiprocessor system 1500 is a point-to-point interconnect system, andincludes a first processor 1570 and a second processor 1580 coupled viaa point-to-point interconnect 1550. As shown in FIG. 15 , each ofprocessors 1570 and 1580 may be multicore processors, including firstand second processor cores (i.e., processor cores 1574 a and 1574 b andprocessor cores 1584 a and 1584 b), although potentially many more coresmay be present in the processors. Each of the processors includes a PCU1575, 1585 or other power management logic to perform processor-basedpower management, including the dynamic inclusion and removal of coresand other processing circuits into and from synchronization domains, toenable dynamic loose lock-step P-state control, as described herein.

Still referring to FIG. 15 , first processor 1570 further includes amemory controller hub (MCH) 1572 and point-to-point (P-P) interfaces1576 and 1578. Similarly, second processor 1580 includes a MCH 1582 andP-P interfaces 1586 and 1588. As shown in FIG. 15 , MCH's 1572 and 1582couple the processors to respective memories, namely a memory 1532 and amemory 1534, which may be portions of system memory (e.g., DRAM) locallyattached to the respective processors. First processor 1570 and secondprocessor 1580 may be coupled to a chipset 1590 via P-P interconnects1562 and 1564, respectively. As shown in FIG. 15 , chipset 1590 includesP-P interfaces 1594 and 1598.

Furthermore, chipset 1590 includes an interface 1592 to couple chipset1590 with a high performance graphics engine 1538, by a P-P interconnect1539. In turn, chipset 1590 may be coupled to a first bus 1516 via aninterface 1596. As shown in FIG. 15 , various input/output (I/O) devices1514 may be coupled to first bus 1516, along with a bus bridge 1518which couples first bus 1516 to a second bus 1520. Various devices maybe coupled to second bus 1520 including, for example, a keyboard/mouse1522, communication devices 1526 and a data storage unit 1528 such as adisk drive or other mass storage device which may include code 1530, inone embodiment. Further, an audio I/O 1524 may be coupled to second bus1520. Embodiments can be incorporated into other types of systemsincluding mobile devices such as a smart cellular telephone, tabletcomputer, netbook, Ultrabook™ or so forth.

One or more aspects of at least one embodiment may be implemented byrepresentative code stored on a machine-readable medium which representsand/or defines logic within an integrated circuit such as a processor.For example, the machine-readable medium may include instructions whichrepresent various logic within the processor. When read by a machine,the instructions may cause the machine to fabricate the logic to performthe techniques described herein. Such representations, known as “IPcores,” are reusable units of logic for an integrated circuit that maybe stored on a tangible, machine-readable medium as a hardware modelthat describes the structure of the integrated circuit. The hardwaremodel may be supplied to various customers or manufacturing facilities,which load the hardware model on fabrication machines that manufacturethe integrated circuit. The integrated circuit may be fabricated suchthat the circuit performs operations described in association with anyof the embodiments described herein.

FIG. 16 is a block diagram illustrating an IP core development system1600 that may be used to manufacture an integrated circuit to performoperations according to an embodiment. The IP core development system1600 may be used to generate modular, re-usable designs that can beincorporated into a larger design or used to construct an entireintegrated circuit (e.g., an SoC integrated circuit). A design facility1630 can generate a software simulation 1610 of an IP core design in ahigh level programming language (e.g., C/C++). The software simulation1610 can be used to design, test, and verify the behavior of the IPcore. A register transfer level (RTL) design can then be created orsynthesized from the simulation model. The RTL design 1615 is anabstraction of the behavior of the integrated circuit that models theflow of digital signals between hardware registers, including theassociated logic performed using the modeled digital signals. Inaddition to an RTL design 1615, lower-level designs at the logic levelor transistor level may also be created, designed, or synthesized. Thus,the particular details of the initial design and simulation may vary.

The RTL design 1615 or equivalent may be further synthesized by thedesign facility into a hardware model 1620, which may be in a hardwaredescription language (HDL), or some other representation of physicaldesign data. The HDL may be further simulated or tested to verify the IPcore design. The IP core design can be stored for delivery to a thirdparty fabrication facility 1665 using non-volatile memory 1640 (e.g.,hard disk, flash memory, or any non-volatile storage medium).Alternately, the IP core design may be transmitted (e.g., via theInternet) over a wired connection 1650 or wireless connection 1660. Thefabrication facility 1665 may then fabricate an integrated circuit thatis based at least in part on the IP core design. The fabricatedintegrated circuit can be configured to perform operations in accordancewith at least one embodiment described herein.

Referring now to FIG. 17 , shown is a flow diagram of a method inaccordance with an embodiment of the present invention. In theembodiment of FIG. 17 , method 1700 may be used to set multiple cores asa collective entity or synchronization domain for purposes of enablingredundant operation on such cores. In addition, method 1700 describes ata high level loose lock-step performance state control as describedherein. As such, method 1700 may be performed by hardware circuitry,firmware, software and/or combinations thereof. In some embodiments,method 1700 may be performed by an OS scheduler in connection with a PCUor other power controller. In other cases, another redundant schedulermay control initiation of a synchronization domain for redundancypurposes as described herein. Also, understand that while embodimentsare described in connection with redundancy-based synchronization, thescope of the present invention is not limited in this regard and inother cases, synchronization operations may be performed in othersituations such as two compute workloads that are to end at the sametime.

As illustrated in FIG. 17 , method 1700 begins first by performingsynchronization operations before a given task is executed. In general,selected cores are allocated to a synchronization domain and after allcores within this domain synchronize, execution begins with all coresstarting together. During the course of such synchronized execution,power management actions may be performed collectively as to all coresof the synchronization domain. As will be further described, optionallysynchronization points may occur during such operation.

As illustrated in FIG. 17 , method 1700 begins by receiving asynchronization indication for two or more cores (block 1710).Understand that this synchronization indication may be triggered byscheduling of an application or other task that is to be executedredundantly on multiple cores to improve accuracy, safety, reliabilityor so forth. In an embodiment, the application may trigger thisindication of synchronization, which may be received by an OS scheduler.In response to this synchronization indication, two or more cores may begrouped into a synchronization domain.

Still with reference to FIG. 17 , to group these two or more corestogether, a synchronization domain indicator may be set for these cores(block 1720). For example, a MSR or other configuration storage mayprovide one or more fields for synchronization domain indicators. In aparticular embodiment, each core may have an entry in such configurationstorage, where a synchronization domain identifier of a synchronizationdomain field can be stored to indicate a given synchronization domainwith which the core is associated. In one embodiment, this field may bea four-bit field, such that 16 different synchronization domains arepossible. When a given field stores a value of, e.g., zero, thisindicates that the given core is not currently a member of a givensynchronization domain. Stated another way, this zero value for thesynchronization domain field indicates that the given core can executeat independent frequency and voltage with respect to other cores. Notethat in embodiments, the synchronization domain indicator can be savedand restored as part of a software thread context switch (e.g., via aXSAVE/XRESTORE operation).

Still referring to FIG. 17 , control next passes to diamond 1725, whereit is determined whether all cores are aligned. This alignment mayinclude synchronization of the cores with respect to operatingparameters including voltage and frequency. Such alignment may furtherinclude clearing the cores such that they may begin operation in acommon state. When it is determined that all cores of thesynchronization domain are aligned, control passes to block 1730 where aworkload, e.g., of a given application, thread or other task underexecution, may be executed on two or more cores of the synchronizationdomain. In some embodiments, this execution may be of a redundantworkload in which two or more cores perform the same task using the samedata. Understand that this execution may occur in loose lock-stepfashion. During the execution, a power management evaluation may occur(block 1740). As will be described further with regard to FIG. 18 below,this power management evaluation may occur periodically duringapplication execution by a PCU or other power controller. In aparticular embodiment, this power management evaluation may occuraccording to a predetermined interval, e.g., approximately every 1millisecond (ms).

Based on this power management evaluation, it can be determined whethera frequency of one or more cores within the synchronization domain is tobe updated (diamond 1750). If so, control passes to block 1755 where aclock generator such as a PLL is instructed to update the frequency ofall the cores in the synchronization domain, such that they maintain thesame operating parameters.

In embodiments used for redundant execution, control optionally passesto diamond 1760 to determine whether a synchronization point in theexecution has been reached (as illustrated by the dashed block). Forexample, a given application that is undergoing redundant execution mayset various synchronization breakpoints at which execution is stoppedand results (such as interim results) compared to ensure that correctoperation inheres in both execution strands.

If it is determined that the synchronization point has not been reachedyet, control passes to back to block 1740. Otherwise if it is determinedthat the synchronization point is reached, control passes to block 1770.At block 1770, results of the redundantly executed task on multiplecores may be synchronized and execution may continue. Note that one orthe other core may reach this synchronization point slightly earlierthan the other core, as the common operating parameter control of thecores happens in a loosely lock-step fashion, such that it is possiblefor a given core to reach a checkpoint some number of cycles prior tothe other core. In an embodiment, the synchronization operation mayinclude commitment of the execution result to the machine state. Forexample, this result (which may be an interim result or a final result)can be committed to the architectural state of the processor.

In some embodiments, if at the synchronization point operation at block1770 it is determined that execution results do not match (or at leastsubstantially match), an error may be raised (not shown for ease ofillustration in FIG. 17 ). For example, this error may be sent to anerror handler, e.g., within the application itself, an operating systemor another location to determine how to resolve the error.

At this point it is determined whether execution (e.g.,) of a redundanttask is completed (diamond 1780). If not, control passes back to block1730 discussed above. Understand while shown at this high level in theembodiment of FIG. 17 , many variations and alternatives are possible.

Referring now to FIG. 18 , shown is a flow diagram of a method inaccordance with another embodiment of the present invention. Morespecifically, method 1800 shown in FIG. 18 is a method for performingpower control of cores within a synchronization domain as describedherein. In embodiments, method 1800 may be performed by hardwarecircuitry, software, firmware and/or combinations thereof. In oneparticular embodiment, method 1800 may be performed by a PCU or otherpower controller. As such, method 1800 is an example representation ofthe power management evaluation described in block 1740 of FIG. 17 .

As illustrated, method 1800 begins by obtaining individual corefrequencies from each core or other processing engine in the processor(block 1810). In one embodiment, this information may be obtained from astorage such as a performance state stack, which stores currentoperating frequency and voltage among other operating parameters foreach core within the processor. In an embodiment in which a core hashardware support for multiple (e.g., two) hardware threads, the multiplethreads can be consolidated to a single value representing the maximumfrequency of the threads of the core. Control next passes to diamond1820 to determine whether there is another synchronization domain forconsideration.

If so (meaning a current synchronization domain is not the lastsynchronization domain), control passes to block 1830 to analyze thecore frequency for each core within the synchronization domain. As onerepresentative example, assume a synchronization domain includes twocores. In this analysis process, the PCU may collect the indicated corefrequency for both of these cores and place them, e.g., in a temporarystorage. Control next passes to block 1840 where a synchronizationdomain frequency can be identified. In a particular embodiment, thissynchronization domain frequency may be identified as the maximum of allcore frequencies for the cores within the synchronization domain. In theexample above with two cores in a synchronization domain, thesynchronization domain frequency may correspond to the core frequencythat is the higher of these two cores. In another case, the utilizationof all cores that belong to the same synchronization domain can becalculated. In this way, a common frequency can be identified to handledependency between cores and avoid performance loss in case ofproducer/consumer threads, for example.

Note also that various consolidation rules can apply. For example, ifone core of the synchronization domain enters a sleep state, votingrights can be maintained (e.g., considering the frequency of core at thesleep state, or alternately ignoring it). Control next passes to block1850 where all cores within the synchronization domain may have theircore frequency set to this synchronization domain frequency (which atthis point is a target frequency). Control loops back to diamond 1820.

When it is determined that there are no further synchronization domainsto be analyzed, control passes to block 1860 where continued powermanagement analysis operations may proceed. As an example, suchoperations may include identifying whether there are any constraints onenabling the processor to operate at the identified core frequencies,such as a thermal constraint, power constraint or so forth. For example,the analysis may include evaluating if the resolved target frequency ofall cores can fit into other processor constraints such as a maximumcurrent load, power budget, or so forth. If this is not the case, theconsolidated (synchronization domain) target frequency can be furtheredscaled down to fit within physical constraints of the processor, thusmaintaining all cores of a synchronization domain locked together.

Note that further in this power management evaluation cycle, a frequencytransition command can be sent to the cores of a given synchronizationdomain to cause the cores to update their frequency to thesynchronization domain frequency. Understand that depending upon theprocessor operation, this synchronization domain frequency may be thatfrequency identified in block 1840 for a given synchronization domain.Or, it may be a lower frequency (e.g., one or more bin frequencies loweror one or more P-states lower), in the case of identification ofprocessor constraints including thermal constraints, power constraintsand so forth. In such constrained environments, the synchronizationdomain frequency acts as a maximum possible frequency, but in the faceof constraints, the actual frequency at which the synchronized cores mayoperate can be lower than this frequency. In different embodiments, thisfrequency transition command may be sent directly to each impacted core(e.g., via a broadcast message) in embodiments in which each coreincludes internal clock and voltage control circuit (such as an internalphase lock loop (PLL) and voltage regulator), via an internal (e.g.,ring) interconnect. In other cases, this command can be sent to anotherentity that provides a core with an operating frequency and/or voltage.Note that some command issue and communication delay may occur, which isacceptable, so long as it is within permitted time bounds.

In this way, embodiments provide fine-grained power control, such thatall cores need not be locked together, while reducing variation suchthat power inefficiencies and longer latencies are avoided. Embodimentsmay thus be used to meet, e.g., FuSa requirements, which may exist invarious system implementations such as Internet of Things (IoT) systems,automotive systems, and so forth. Understand while shown at this highlevel in the embodiment of FIG. 18 , many variations and alternativesare possible.

Referring now to FIG. 19 , shown is a block diagram of a system inaccordance with an embodiment of the present invention. Morespecifically, a portion of a system 1900, which may be any of manydifferent types of computing devices ranging from small portabledevices, IoT systems, automotive systems, to full computing systems isshown, including a plurality of SoCs 1910 and 1910-2-1910-N, each ofwhich may be a multicore processor or any other type of SoC.

As illustrated, to receive configuration information, includingfrequency and voltage information, platform-level power, thermal andother budgeting information and so forth, an interface 1965 couples SoC1910 to storage(s) 1970. Understand that interface 1965 may be any typeof interconnect or other interface mechanism. As an example, portions ofthe interface may be internal to one or more of SoC 1910 and storage(s)1970. Still further, portions may be implemented, e.g., as traces orother interconnects on a circuit board that couples SoC 1910 andstorage(s) 1970 together.

As illustrated, representative SoC 1910 includes multiple cores 1915i-1915 n, each of which may be independently controlled to operate inone or more different P-states and/or C-states. As illustrated inrepresentative core 1915-1, an MSR 1918 is present. Of course each core1915 may include a corresponding MSR. In embodiments herein, MSR 1918may include a synchronization domain field to indicate whether the givencore is included in a synchronization domain (and further including anidentity of such synchronization domain). Cores 1915 (generically)couple to a power control unit 1920. In embodiments, PCU 1920 mayperform various power management techniques, including dynamic voltageand frequency control. Still further, PCU 1920 may dynamically controlone or more cores 1915 to enter into and exit from synchronizationdomains. In the embodiment shown, PCU 1920 includes a power controlcircuit 1922 which may perform various power management activities.Still further, PCU 1920 includes a synchronization circuit 1924 which,responsive to control information received from power control circuit1924, may control entry of cores into and exit from a givensynchronization domain. For example, synchronization circuit 1924,responsive to receipt of a synchronization domain indication, may causemultiple cores 1915 to enter into a synchronization domain such that thecores may operate in loose lock-step fashion as described herein. In anembodiment, synchronization circuit 1924, via power control circuit 1922may read information from MSR 1918, including a synchronization domainindicator within the synchronization domain field to identify givencores of a synchronization domain and to perform the dynamic looselock-step frequency and voltage control described herein. Inembodiments, note that synchronization circuit 1924 may further causethis synchronization domain indicator to be written into correspondingMSRs 1918 upon initialization of a given synchronization domain.

Still with reference to FIG. 19 , SoC 1910 further includes aconfiguration storage 1935, which may store a variety of configurationinformation for operation of the processor and power managementoperations, including the synchronization domain control describedherein. To this end, e.g., one or more of a BIOS (and/or a dynamic powerand thermal framework (DPTF)) 1972 and an OS 1975 may provideinformation via interface 1965, for storage into configuration storage2135.

As further illustrated, in FIG. 19 , an embedded controller 1980 couplesto SoC 1910 via an interconnect 1985, which in an embodiment may be aplatform environment control interface (PECI) interconnect. Inembodiments, embedded controller 1980 may control platform-level powermanagement and in some cases may be implemented as a power managementintegrated circuit (PMIC). Furthermore, based upon detected operatingparameters of system 1900, embedded controller 1980 may communicateplatform constraint information, which may be provided to PCU 1920 (andmore specifically power control circuit 1922). Based on suchinformation, power control circuit 1922 may cause synchronizationcircuit 1924 to reduce a synchronization domain frequency from a targetsynchronization domain frequency to a lower synchronization domainfrequency (e.g., one or more bin frequencies and/or P-state frequencieslower) to accommodate the given platform and/or processor constraint.Understand while shown at this high level in the embodiment of FIG. 19 ,many variations and alternatives are possible.

Referring now to FIG. 20 , shown is a block diagram of a system inaccordance with another embodiment of the present invention. Asillustrated in FIG. 20 , system 2000 may be any type of computing systemthat includes a processor 2010. Processor 2010 receives one or moreoperating voltages from a voltage regulator 2040. In execution,processor 2010 may execute an operating system 2050 that includes ascheduler component 2055. In some cases, scheduler 2055 may beresponsible for initiating core allocations into a given synchronizationdomain when called for by a particular workload to be executed onprocessor 2010.

In the embodiment shown in FIG. 20 , processor 2010 is a multicoreprocessor including a plurality of cores 2012 ₁-2012 _(M). Each core maybe independently controlled to receive an independent operating voltageand frequency by way of corresponding fully integrated voltageregulators (FIVRs) 2014 ₁-2014 _(M) and PLL's 2016 ₁-2016 _(M).

As further illustrated, processor 2010 also includes a power managementunit 2030 that itself includes a synchronization circuit 2035. Inembodiments herein, synchronization circuit 2035, in response to anindication of synchronization for multiple cores, e.g., received fromscheduler 2055, may cause multiple cores 2012 to be allocated to a givensynchronization domain and controlled to operate at a common operatingpoint (e.g., voltage and frequency) in a loose lock-step manner asdescribed herein.

To initiate synchronization operation, scheduler 2055 may take allthreads that belong to the same synchronization domain and schedule themon a given subset of cores 2012. When scheduling, it may write, e.g., ina MSR, domain information (including a domain number). This informationis communicated to power management unit 2030 (e.g., to synchronizationcircuit 2035). In response to this information, synchronization circuit2035 may manage such core subset as a single synchronization domain. Atthis point, cores 2012 within this synchronization domain may wait fortheir frequencies to align (either via an indication sent bycore-to-core communication or via feedback from power management unit2030). Then execution within the synchronization domain may begin on thesubset of cores 2012 within the synchronization domain. Understand whileshown at this high level in the embodiment of FIG. 20 , many variationsand alternatives are possible.

The following examples pertain to further embodiments.

In one example, a processor comprises: a first core; a second core,where the first core and the second core are to execute a taskredundantly; a configuration register to store a first synchronizationdomain indicator to indicate that the first core and the second core areassociated with a first synchronization domain; and a power controllerincluding a synchronization circuit to cause a dynamic adjustment to afrequency of at least one of the first core and the second core to causethe first core and the second core to operate at a common frequency,based on the first synchronization domain indicator.

In an example, in response to the first synchronization domainindicator, the power controller is to cause the first core and thesecond core to operate at a synchronization domain frequency that is amaximum of a first frequency of the first core and a second frequency ofthe second core.

In an example, the synchronization circuit is to dynamically associatethe first synchronization domain indicator with the first core and thesecond core in response to scheduling of a redundant application to thefirst core and the second core.

In an example, the synchronization circuit is to dynamicallyde-associate the first synchronization domain indicator with the firstcore and the second core after completion of the redundant application,and where after the de-association the first core and the second coreare to operate at differing frequencies.

In an example, the processor further comprises a ring interconnect tocouple the first core and the second core to the power controller, wherethe power controller is to send a frequency transition command to thefirst core and the second core to cause the first core and the secondcore to operate at the common frequency.

In an example, via the ring interconnect, the first core and the secondcore are to receive the frequency transition command at different timeinstants such that the first core and the second core begin operation atthe common frequency asynchronously within a time bound duration.

In an example, one of the first core and the second core is to completethe redundant execution of the task prior to the other of the first coreand the second core, and within a predetermined time duration.

In an example, the processor further comprises a redundancy circuit tocompare a first result of the redundant execution of the task on thefirst core to a second result of the redundant execution of the task onthe second core, and raise an error if the first result does not atleast substantially match the second result.

In an example, the redundancy circuit is to enable the first result tobe committed in response to the first result matching the second result.

In an example, the configuration register is to store anon-synchronization domain indicator for one or more other cores toindicate that the one or more other cores can operate at independentfrequencies with respect to each other.

In an example, the configuration register includes a plurality of coreportions each associated with a core, where each of the plurality ofcore portions includes a synchronization domain field to store asynchronization domain indicator for the associated core.

In another example, a method comprises: during execution of anapplication, receiving an indication that a first set of cores of amulticore processor are to be placed into a first synchronizationdomain; identifying a current core frequency of each of the first set ofcores; identifying a first synchronization domain frequencycorresponding to a maximum one of the current core frequency of each ofthe first set of cores; and causing the first set of cores to operate atthe first synchronization domain frequency.

In an example, the method further comprises receiving the indication inresponse to an initiation of a task of the application to be executedredundantly on the first set of cores.

In an example, the method further comprises dynamically de-associatingthe indication from the first set of cores after completion of theredundant task, and where after the de-association at least some of thefirst set of cores are to operate at differing frequencies.

In an example, the method further comprises sending, from a powercontroller via an interconnect that couples the power controller to thefirst set of cores, a frequency transition command to the first set ofcores to cause the first set of cores to operate at the firstsynchronization domain frequency and in response to the frequencytransition command, the first set of cores are to operate at the firstsynchronization domain frequency in loose lock-step fashion.

In an example, the method further comprises, after receiving thefrequency transition command, executing a redundant task of theapplication on the first set of cores, where a first core of the firstset of cores completes the redundant task prior to and within apredetermined time duration of completion of the redundant task on asecond core of the first set of cores.

In an example, the method further comprises: identifying at least oneconstraint on the multicore processor and determining a secondsynchronization domain frequency less than the first synchronizationdomain frequency; and causing the first set of cores to operate at thesecond synchronization domain frequency.

In another example, a computer readable medium including instructions isto perform the method of any of the above examples.

In another example, a computer readable medium including data is to beused by at least one machine to fabricate at least one integratedcircuit to perform the method of any one of the above examples.

In another example, an apparatus comprises means for performing themethod of any one of the above examples.

In another example, a system comprises a multicore processor, a platformcontroller, and a system memory. The multicore processor may have aplurality of cores each having a first storage to store asynchronization domain indicator having a first value to indicate thatthe core is to operate at an independently controlled performance stateand a second value to indicate that the core is associated with asynchronization domain and to operate at a synchronized performancestate with one or more other cores of the plurality of cores, themulticore processor further including a power controller including asynchronization circuit to cause a dynamic adjustment to a frequency ofat least one of the plurality of cores to cause the at least one core tooperate at the synchronized performance state, in response to the secondvalue of the synchronization domain indicator. The platform controllermay be coupled to the multicore processor to communicate platformenvironmental information to the multicore processor, and the systemmemory also may be coupled to the multicore processor.

In an example, the synchronization circuit is to cause the at least onecore and a second core to operate at the synchronized performance stateto enable execution of a redundant task on the at least one core and thesecond core in loose lock-step, and after the execution of the redundanttask to cause the at least one core and the second core to operate atindependent performance states.

In an example, in response to the synchronization domain indicatorhaving the second value, the power controller is to cause the at leastone core and the second core to operate at one of: a firstsynchronization domain frequency that is a maximum of a first frequencyof the at least one core and a second frequency of the second core; anda second synchronization domain frequency that is less than the firstsynchronization domain frequency in response to identification of aconstraint on the multicore processor.

In another example, an apparatus comprises: means for receiving anindication that a first set of cores of a multicore processor are to beplaced into a first synchronization domain; means for identifying acurrent core frequency of each of the first set of cores; means foridentifying a first synchronization domain frequency corresponding to amaximum one of the current core frequency of each of the first set ofcores; and means for causing the first set of cores to operate at thefirst synchronization domain frequency.

In an example, the apparatus further comprises means for dynamicallyde-associating the indication from the first set of cores aftercompletion of a redundant task, and where after the de-association atleast some of the first set of cores are to operate at differingfrequencies.

In an example, the apparatus further comprises means for sending afrequency transition command to the first set of cores to cause thefirst set of cores to operate at the first synchronization domainfrequency and in response to the frequency transition command, the firstset of cores are to operate at the first synchronization domainfrequency in loose lock-step fashion.

In an example, the apparatus further comprises means for executing aredundant task on the first set of cores, where a first core of thefirst set of cores completes the redundant task prior to and within apredetermined time duration of completion of the redundant task on asecond core of the first set of cores.

In an example, the apparatus further comprises: means for identifying atleast one constraint on the multicore processor and determining a secondsynchronization domain frequency less than the first synchronizationdomain frequency; and means for causing the first set of cores tooperate at the second synchronization domain frequency.

Understand that various combinations of the above examples are possible.

Note that the terms “circuit” and “circuitry” are used interchangeablyherein. As used herein, these terms and the term “logic” are used torefer to alone or in any combination, analog circuitry, digitalcircuitry, hard wired circuitry, programmable circuitry, processorcircuitry, microcontroller circuitry, hardware logic circuitry, statemachine circuitry and/or any other type of physical hardware component.Embodiments may be used in many different types of systems. For example,in one embodiment a communication device can be arranged to perform thevarious methods and techniques described herein. Of course, the scope ofthe present invention is not limited to a communication device, andinstead other embodiments can be directed to other types of apparatusfor processing instructions, or one or more machine readable mediaincluding instructions that in response to being executed on a computingdevice, cause the device to carry out one or more of the methods andtechniques described herein.

Embodiments may be implemented in code and may be stored on anon-transitory storage medium having stored thereon instructions whichcan be used to program a system to perform the instructions. Embodimentsalso may be implemented in data and may be stored on a non-transitorystorage medium, which if used by at least one machine, causes the atleast one machine to fabricate at least one integrated circuit toperform one or more operations. Still further embodiments may beimplemented in a computer readable storage medium including informationthat, when manufactured into a SoC or other processor, is to configurethe SoC or other processor to perform one or more operations. Thestorage medium may include, but is not limited to, any type of diskincluding floppy disks, optical disks, solid state drives (SSDs),compact disk read-only memories (CD-ROMs), compact disk rewritables(CD-RWs), and magneto-optical disks, semiconductor devices such asread-only memories (ROMs), random access memories (RAMs) such as dynamicrandom access memories (DRAMs), static random access memories (SRAMs),erasable programmable read-only memories (EPROMs), flash memories,electrically erasable programmable read-only memories (EEPROMs),magnetic or optical cards, or any other type of media suitable forstoring electronic instructions.

While the present invention has been described with respect to a limitednumber of embodiments, those skilled in the art will appreciate numerousmodifications and variations therefrom. It is intended that the appendedclaims cover all such modifications and variations as fall within thetrue spirit and scope of this present invention.

What is claimed is:
 1. An apparatus comprising: a first core comprising:a fetch unit to fetch instructions; a decode unit to decode theinstructions; a renamer to rename registers to facilitate out of orderexecution; an integer execution unit to execute arithmetic and logicoperations; and a vector execution unit to execute single instructionmultiple data (SIMD) operations; memory to store a first indicator, thefirst indicator to have a first value to indicate that the first coreand a second core are to redundantly execute a first task; and acontroller to cause the first core and the second core to operate at acommon frequency to redundantly execute the first task based at least inpart on the first value of the first indicator.
 2. The apparatus ofclaim 1, further comprising a cluster comprising the first core and thesecond core.
 3. The apparatus of claim 2, further comprising a thirdcore, wherein the controller is to cause the third core to execute asecond task different than the first task.
 4. The apparatus of claim 3,wherein the third core is heterogeneous to the first core.
 5. Theapparatus of claim 3, wherein the controller is to cause the third coreto execute the second task while the first core and the second coreexecute the first task redundantly.
 6. The apparatus of claim 1, whereinthe controller is to cause the first core and the second core to operateat independent frequencies based at least in part on a second value ofthe first indicator.
 7. The apparatus of claim 1, wherein the apparatusis to perform a functional safety application.
 8. The apparatus of claim1, wherein the controller comprises a power controller.
 9. The apparatusof claim 8, wherein the power controller is to cause at least the firstcore to perform dynamic frequency scaling.
 10. The apparatus of claim 8,wherein the power controller is to cause at least the first core toenter into a retention mode in which a retention voltage is provided toat least the first core.
 11. The apparatus of claim 1, wherein thedecode unit is to decode ARMv8 instruction set architecture (ISA)instructions.
 12. The apparatus of claim 1, further comprising aredundancy circuit to compare a first result of the redundant executionof the first task on the first core to a second result of the redundantexecution of the first task on the second core, and raise an error ifthe first result does not at least substantially match the secondresult.
 13. The apparatus of claim 1, wherein the memory comprises atleast one register to store the first indicator.
 14. A system on chipcomprising: a central processing unit (CPU) comprising: a first core; asecond core, wherein the first core and the second core are to execute afirst task redundantly, wherein the second core is to redundantlyexecute the first task within 1 to 10,000 execution cycles of executionof the first task by the first core; a graphics processing unit (GPU)coupled to the CPU, the GPU comprising at least one graphics engine toperform graphics processing; memory to store a first indicator, thefirst indicator to have a first value to indicate that the first coreand the second core are to redundantly execute the first task; and acontroller to cause the first core and the second core to operate at acommon frequency to redundantly execute the first task based at least inpart on the first value of the first indicator.
 15. The system on chipof claim 14, wherein the controller is to cause the first core and thesecond core to operate at independent frequencies based at least in parton a second value of the first indicator.
 16. The system on chip ofclaim 15, wherein the CPU further comprises at least one cluster, the atleast one cluster comprising: the first core; the second core; a thirdcore; a fourth core; and a shared cache memory.
 17. The system on chipof claim 14, further comprising a redundancy circuit to compare a firstresult of the redundant execution of the first task on the first core toa second result of the redundant execution of the first task on thesecond core.
 18. An apparatus comprising: a first core; a second core; astorage to store a first indicator, wherein the first indicator is toindicate that the first core and the second core are to redundantlyexecute a first task when the first indicator has a first value; and acontroller coupled to the storage, wherein the controller is to causethe first core and the second core to be switched between redundancy inlockstep operation and independent core operation, wherein in theredundancy in lockstep operation the first core and the second core areto operate at a common frequency to redundantly execute the first taskbased at least in part on the first value of the first indicator, andwherein in the independent core operation the first core and the secondcore are to operate at independent frequencies based at least in part ona second value of the first indicator.
 19. The apparatus of claim 18,further comprising a power controller comprising the controller.
 20. Theapparatus of claim 18, further comprising a security processor.